1. Field of the Invention
This invention relates to motor vehicles, and more particularly to an integrated electronic shift and parking brake system, including a security interlock in one embodiment, for a motor vehicle, especially one whose prime mover comprises an electric traction motor.
2. Background Information
A known vehicle that is powered by an electric traction motor comprises a shifter that is operated by a driver of the vehicle to select one of several positions that establish different modes of operating the motor in relation to the vehicle drivetrain. A representative set of positions comprises PARK, REVERSE, NEUTRAL, DRIVE, and ECONOMY positions. In both PARK and NEUTRAL positions, the motor is unable to propel the vehicle. In REVERSE position, the motor can act through the drivetrain to deliver traction torque for propelling the vehicle in reverse. DRIVE and ECONOMY positions represent two different forward drive positions in which the motor can deliver traction torque to propel the vehicle forward.
As the shifter is moved to different positions, a cable couples the shifter motion to a parking pawl on the motor, turning the pawl in correspondence with the shifter motion. The turning of the parking pawl also turns an attached sensor which is electrically coupled to a traction control module that controls the motor. The sensor sends an electric signal to the module corresponding to the position selected by the shifter. The module contains software which acts upon the sensor signal to operate the motor in accordance with the position selected by the shifter.
The known vehicle also comprises a parking brake system that is operated by a handbrake lever to selectively apply and release one or more wheel brakes. When a driver operates the handbrake lever to apply the parking brake, the lever pulls a cable that causes drum brakes of the two rear of wheels of the vehicle to be applied. When the driver releases the parking brake, a spring mechanism releases the drum brakes so that they cease to be applied.
When the vehicle is stopped, the parking brake may be applied to prevent the vehicle from rolling, for example when the vehicle is parked on an inclined surface. The parking brake may also be applied to slow the vehicle when the vehicle is in motion.
Documents mentioned in an Information Disclosure Statement were developed in consequence of a novelty search with respect to the present invention, and they are believed representative of the state of the art.